I also found that the bike cruises better with the 19-tooth. I can now run down the interstate just fine, but it's still not a fun way to ride on such a smal bike. I figured it out mathematically, and the extra tooth gives you about 3-4 mph more in top gear

I was cruising between 70 and 75. I had the bike at 80mph before I changed the sprocket. I still had a little left. I think I could do at least 85 now. Trouble is, the bike is too light to be riding that fast. It's much more comfortable on secondary roads where people drive between 45 and 65. I didn't see many other bikes on the interstate either, but I see lots of them on the backroads. Some friends of mine belong to a Gold Wing club and I ride with them sometimes. Their bikes could easily cruise at 100, but they detest expressways and pick routs though the backroads. It's nice to know that I could get on the interstate for short stretches If I have to, like an occasional connector or shortcut. I can now go anywhere in the country, and I plan to do some extended road trips very soon.